It said lists in some voting districts swelled by more than 10,000 names in a 48-hour period, or the addition of about 150 voters a second.

“This is just impossible,” said party official Douglas Mwonzora. He said a copy of one Harare district list was obtained on a Monday earlier this month. Two days later, a revised copy showed an additional 11,890 voters on the list.

In other districts the names of active party members were missing or misspelled, making them ineligible to vote, raising fears of voting fraud being planned by officials loyal to President Robert Mugabe’s party, he said.

The official voters’ registry has denied tampering with the lists and insists it is just collating data in batches.

A new drive to register voters began Monday, following weeks of campaigning by all political groups for eligible voters not yet listed to have their details added to the nationwide roll containing 5.7 million names in a population of 13 million, slightly less than half of whom are under the voting age of 18.

Tsvangirai’s Movement for Democratic Change party, in a shaky coalition with Mugabe brokered by regional leaders after the last violent and disputed elections in 2008, said even Theresa Makone, its co-minister of Home Affairs in charge of voter registration, saw her name was missing in her area.

Under the coalition agreement, Tsvangirai’s party shares control of that ministry that is also responsible for the nation’s police dominated by Mugabe loyalists. Makone has had little influence over police commanders and senior government officials who have repeatedly vowed their allegiance to Mugabe.

Makone has told her district supporters that irregularities in their voters’ list were “a tip of the iceberg” in what she suspected was happening countrywide to skew voting. Past elections since 2000 have been marred by allegations of vote rigging.

Tsvangirai on Sunday began a diplomatic offensive to garner the backing of regional leaders to ensure fair conditions are in place for elections planned between July and September that include large scale corrections to the voters’ lists. Last month, the state Electoral Commission said in a continuing clean-up exercise it had removed the names of 350,000 dead voters who had appeared on previous lists.

Tsvangirai’s party also accuses Mugabe of resisting reforms to sweeping media sweeping media and security laws demanded by regional mediators in the run-up to polling.

It says “hate speech” against Tsvangirai and his colleagues in the former opposition by the state broadcast monopoly and the main newspapers loyal to Mugabe has not been reined in and the party has been denied fair access to the state broadcaster, the only source of information to many impoverished, rural voters.

Tsvangirai met with South African President Jacob Zuma, the chief Zimbabwe mediator, on Sunday before heading to Tanzania to meet with President Jakaya Kikwete, current chair of a three nation Southern African Development Community (SADC) “troika” on regional disputes.

Tsvangirai’s office said he has called for an urgent regional summit on long delayed democratic reforms in Zimbabwe.

Zuma told Tsvangairia that SADC and the continent-wide African Union organization “will do everything in their power to ensure a free and fair poll in Zimbabwe,” said Luke Tamborinyoka, Tsvangirai’s spokesman.